JP6234925B2 - Yield control method and intermediate product used in the method - Google Patents

Description

  The present invention relates to a method for controlling retention related to forming fabrics in a papermaking process. Another subject of the invention is the intermediate product intended to be added to the fiber suspension used for papermaking and the use of the material for the intermediate product.

  In the papermaking process, a number of papermaking chemicals are used for process control and to give the paper the necessary properties. Papermaking chemicals are administered to the wet end of the paper machine by incorporating the aqueous fiber suspension into the aqueous fiber suspension before feeding it from the headbox to the forming fabric. The purpose is to adsorb chemicals onto the surface of the fiber by electrostatic forces.

  The main problem with using some papermaking chemicals adsorbed on the fiber surface by similar machines is how to achieve a yield and even a uniform distribution on the fiber surface. Almost all the additives need to compete for free bond (anionic, cationic and neutral) sites on the fiber surface. In most cases, this results in incomplete yield and / or uneven distribution of the drug on the fiber surface. As a result, the quality of the finished paper is lowered, and it is considered that the problem of operability occurs in the paper machine. In addition to inadequate yield and distribution, the combination of several reactive additives can cause adverse interaction reactions between various papermaking chemicals, thus reducing their functionality and effectiveness.

  A number of special papermaking chemicals (yield improvers) to improve the yield of papermaking chemicals and the fines present in the fiber suspension (the amount of material retained in the formed web) (Retention chemicals)) has been used in the past. Papermaking chemicals that have a low yield on the fiber surface can accumulate in the white water system and adhere to the paper machine surface as contaminants or can adhere to each other to form agglomerates. Such agglomeration can cause web breaks and spots on the paper produced. In contrast, good yield reduces the amount of fibers, fillers and other chemicals that pass through the paper machine's short circulation and accumulate in the process system.

  Papermaking chemicals used in large quantities are a major cause of harmful sedimentation contaminants and derived drivability and quality problems in paper machines. Examples of such papermaking chemicals include sizing agents, fillers, and chemicals that impart wet paper strength and dry paper strength.

  The mechanism of drug yield is to bind small particles (eg, filler particles) as larger agglomerated particles that can be maintained by the wet fibrous web on the forming fabric. This agglomeration can be achieved in most cases by the use of various retention aids which are water soluble polymers, ie polyelectrolytes.

  In a dual polymer system, two polyelectrolytes are used simultaneously. Those problems in practical use are that it is difficult to find an optimum condition, and small process changes may have a great influence. Such dual systems work by forming attachment points for long chain polymers by adsorbing shorter chain length polymers to the surface of the filler particles. In the first stage, aggregation occurs through the formation of mosaics, and in the second stage, aggregation occurs due to crosslinking.

Typical microparticle systems are for example
Cationic starch / polyacrylamide + colloidal silica (for example, sold under the trademark “Compozil”),
Polyacrylamide + bentonite (e.g., sold under the trademark "Hydrocol"),
It is.

  As the first step of such a prior art process, after adding the cationic polymer to the paper pulp, just before the headbox, very fine material (particle size 250 nm to 10 μm) and in most cases negative to high order Charged (about 1 meq / g) microparticles are added. In this way, microaggregated particles are formed, which have a strong tendency to aggregate even after the aggregated particles have been broken. This can be seen because white water has a strong aggregating ability. The aggregated particles that are formed are very small (compared to previous yield improvers) and this effect is further increased after aggregation. Agglomeration at the microscale provides high porosity to the web, thus improving dewatering, increasing solids after the press section and reducing drying energy demand.

  The problem to be solved by the present invention is to provide an overall improvement in the yield of fibers and papermaking chemicals in the fibrous web formed on the forming fabric in the papermaking process. Such improvements are believed to reduce the amount of fibers and chemicals that pass through the short circulation, deposits on the surface of the tubes and chambers along the circulation path, and agglomerates that eventually become soiled paper stains. It is done. Furthermore, it is an object of the present invention to control the yield of a particular papermaking chemical so as to allow control of the yield of a plurality of chemicals contained in the papermaking suspension that are interrelated.

The solution according to the invention is at least:
Preparing a fiber suspension for papermaking;
A step of preparing a slurry containing fine cellulose fibers, wherein the specific surface area of the fine cellulose fibers is larger than the specific surface area of the fibers of the fibrous suspension;
Adding at least one papermaking chemical to the slurry, adsorbing the papermaking chemical on the fine cellulose fibers to form an intermediate product;
Incorporating the intermediate product into the fiber suspension for papermaking; and feeding the fiber suspension containing the intermediate product onto a forming fabric.

  Improvements in the yield of fiber and papermaking chemicals on the forming fabric and in the subsequent pressing section are due to a decrease in fiber and papermaking chemical concentrations in the short cycle of the paper machine / paperboard machine, and therefore Appears as suspended agglomerate formation and reduced solid material deposition in other parts.

  Without being bound by any theory, the higher the specific surface area of the fine fibers used in the intermediate product compared to the beaten pulp used in the basic papermaking suspension, the greater the amount of papermaking It is believed that it becomes possible to adsorb chemicals, especially cationic papermaking chemicals, onto the fiber surface. This is particularly beneficial for use in the present invention, especially since it applies to very fine fibers such as MicroFibrillated Cellulose (MFC) fibers that have a huge open active surface.

  In accordance with the teachings of the present invention, a large free surface is provided for adsorption / absorption of one or more papermaking chemicals. This is done by providing a large specific surface area in the aqueous slurry of fibers. These are dry cuts, or more beneficially fibers having a fiber diameter of less than about 200 nm, preferably less than about 50 nm, most preferably less than about 20 nm, and fiber lengths of 100 nm to 200 μm, preferably 100 nm to 10 μm, or It can be a fibril.

  Here, the definition of microfibrillated cellulose (MFC) refers to a fiber material composed of cellulose fibers in which individual microfibrils or microfibril aggregates are separated from one another. The fibers of MFC are usually very thin, the fiber diameter is about 20 nm, and the fiber length is usually 100 nm to 10 μm. As used herein, the definition of MFC also includes so-called NanoFibrillated Cellulose (NFC). However, as described above, the present invention allows fibrils to have larger diameters up to 200 nm and longer and longer fiber lengths up to 200 μm and more. Depending on the manufacturing method, a slight amount of longer and thicker fibers may remain.

  Longer fibers, referred to herein as fines, that can be used are those that pass through the 200 mesh screen of the Bauer-McNett device. Almost all fibers are shorter than 0.2 mm. Usually, pulp slurries containing such fines also contain indefinite amounts of MFC or NFC.

As described above, the term dry cut refers to a wood fiber cut from a wood material in a dry state. They have a wide open active surface capable of adsorbing papermaking chemicals. The pulp slurry obtained by this method contains dry cut fibers, for example,
Dry cutting method (with whimill mill type device),
Compactor cutting method,
Conical extrusion,
Can be obtained by:

  The pulp slurry thus obtained contains fibers having an average length of less than 1 mm. Such a relatively coarse fine fraction usually also contains finer fibers.

  Various fibers or fibrils having a specific surface area greater than that of the basic paper suspension can also be used as a mixture. Furthermore, the effectiveness of the pulp slurry used as an adsorbent matrix for papermaking chemicals depends on the proportion of MFC, fiber fines and dry cuts in the pulp slurry. The ratio of MFC, fiber fines and dry cuts in the pulp slurry depends on, for example, the raw material of the pulp slurry (cellulosic raw material or lignocellulosic raw material) and the production method (chemical pulp, chemimechanical pulp or mechanical pulp) Determined.

  According to one embodiment of the present invention, a single papermaking chemical is adsorbed to cover the applicable surface of fibrillated cellulose fibers. Alternatively, the first papermaking chemical may be adsorbed on a portion of the applicable surface of the fibrillated cellulose fiber and then the second papermaking chemical is applied to the applicable surface of the fibrillated cellulose fiber. Adsorb to the remaining part. This makes it possible to control the relative amount of chemicals contained in the intermediate product and the chemicals that are ultimately maintained on the forming fabric.

  In general, fibrillated cellulose fibers form the main component of the intermediate product. When weighed, these amounts are determined in the product by a papermaking chemical (several sizing agents selected from hydrophobic sizing agents, wet strength enhancing sizing agents and dry strength enhancing sizing agents, agglomeration improving agents and fillers). It may be at least as large as, and preferably greater than, the total amount.

  It is preferred that the weight ratio of adsorbing cellulose fibers and one or more papermaking chemicals in the intermediate product varies between 20: 1 and 1: 1.

  After the papermaking chemical is adsorbed to the fibers in the pulp slurry, the fibers can be agglomerated by using a polyelectrolyte or a chemical having a similar mechanism of action. This agglomeration is very effective due to the size and active surface of the fibers used in the present invention, especially the MFC fibers. After this, an intermediate product containing pre-agglomerated fibers can be administered to the fiber paper suspension at the wet end of the paper machine.

  According to another embodiment of the present invention, one or more additional papermaking chemicals are added to the papermaking fiber before or after the intermediate product is incorporated into the papermaking fiber suspension. In the suspension. In this way, undesirable chemical interaction between the intermediate product and the papermaking chemical introduced into the further papermaking chemical can be reduced or completely avoided. Also, the yield of the further papermaking chemical can be increased as a result.

  A significant advantage of the present invention over prior art methods is that a much larger amount of papermaking chemical can be adsorbed onto the fiber suspension at the wet end of the papermaking machine. This is because, on the one hand, after the papermaking chemicals (adsorbants) are adsorbed onto the surface of the fine cellulose fibers (adsorbate), the fibers are used as intermediate products in the wet end of the papermaking machine. By adding them to the fibrous suspension or, on the other hand, the chemicals in a separate step so that they do not interact with the chemicals introduced as part of the intermediate product. It became possible by adding to.

This is important for papermaking chemicals that are advantageously used in large quantities during standard papermaking processes. These papermaking chemicals include sizing agents such as hydrophobic sizing agents (for example, alkyl ketene dimer (AKD) or alkenyl succinic acid anhydride (ASA)); cationic polymers Aggregation promoters such as electrolytes or cationic starch, anionic polyacrylamide, bentonite; wet or dry paper strength enhancers such as starch or resin; and clay, PCC (precipitated calcium carbonate) and CaCO ₃ A filler is mentioned.

  In general, papermaking chemicals herein refer to all non-fibrous materials used during the papermaking process. Examples of papermaking chemicals include process chemicals and functional chemicals. Papermaking chemicals may be cationic, neutral or anionic. Functional papermaking chemicals affect the properties of the paper / paperboard that is prepared. These include, but are not limited to: chemicals, fillers, chemicals, pigments, special pigments, bentonite, dye colors, fluorescent dyes, resistance to sizing, wet or dry paper strength. Examples thereof include fatty fluorochemicals. Papermaking chemicals include those that improve the operability of the paper / board web or fiber fabric in the wet or dry end of the paper / board manufacturing process and usually indirectly improve the properties of the paper / paperboard prepared. Is mentioned. These include, but are not limited to, alums, retention aids, chemicals that remove water, chemicals that promote dispersion, and chemicals that inhibit gum or foam formation.

  Particularly preferred papermaking chemicals in the present invention are hydrophobic sizing agents such as sizing agents such as alkyl ketene dimers (AKD) or alkenyl succinic anhydrides (ASA), and wet paper strength enhancing sizing agents and / or dry paper strength enhancing agents. A sizing agent such as PolyAmidoAmine Epichlorohydrin (PAAE).

  A preferred method of combining the intermediate product with the main papermaking suspension is to use circulating white water to dilute the suspension before feeding the suspension from the headbox to the forming fabric. Including the addition of intermediate products to the short circulation of the paper machine. Most preferably, the intermediate product is added to the diluted suspension just before the headbox. Generally for dilution of paper suspensions, the consistency of the fiber suspension is at most 1.2% by weight, preferably in the range of 0.1% to 0.8% by weight, before entering the headbox. Can be diluted to

  However, it is also possible to add the intermediate product to the fiber suspension separately from the short circulation. In this case, the intermediate product may be added to the undiluted higher viscosity stock prior to the circulating white water inlet.

  With respect to the preparation of the intermediate product, papermaking chemicals may be added to the slurry of MFC or other fine cellulosic fibers to form an intermediate product by use of a mixer, advantageously a jet jet mixer. Mixing can take place before or simultaneously with injecting the intermediate product into the fiber suspension. Preferably, after dilution of the suspension with short circulating white water, the intermediate product is injected into the suspension by use of a jet mixer.

  Jet jet mixers, such as Trumpjet type mixers, are useful for use in the present invention because high shear can be created to disperse the intermediate product into the main fiber suspension flow. This is important for achieving proper mixing and avoiding MFC aggregation, which would otherwise occur very rapidly.

  Before adding one or more papermaking chemicals to form an intermediate product, the fiber content in the aqueous slurry is 1% to 5% by weight, preferably 2% to 3% by weight. be able to.

  Alternatively, the intermediate product may be added to the circulating white water before using the white water to dilute the fiber suspension. The fiber content of white water can be as low as 0.05% to 0.2% by weight and does not increase appreciably with the addition of intermediate products. In this embodiment, an injection jet mixer may be used for mixing and injection.

  It is preferred to combine the fibers with papermaking chemicals in wet form. For example, AKD can be applied as a 15 wt% aqueous dispersion that can be added to an aqueous slurry of MFC. However, MFC or other fine cellulose fibers can be mixed with papermaking chemicals in dry form and then the mixture can be converted to a slurry by adding water.

  Main fiber suspensions for papermaking are used alone or in a mixture, such as chemical pulp such as kraft pulp or sulfite pulp, Chemi thermomechanical pulp (CTMP), thermomechanical pulp (TMP), mechanical pulp Or the recycled pulp etc. may be included. The terms paper, papermaking, papermaking process and papermaker each refer not only to paper, but also to paperboard and cardboard.

  The intermediate product according to the invention consists of a cellulosic or lignocellulosic slurry comprising fibrillated cellulose fibers and at least one papermaking chemical adsorbed on the fibrillated cellulose fibers. The intermediate product is intended to be added to the fiber suspension before the suspension enters the paper machine headbox.

  When measured by weight, the amount of fibrillated cellulose fibers in the intermediate product is preferably at least as great as, and more preferably greater than, the total amount of papermaking chemicals in the intermediate product.

  The intermediate product preferably comprises microfibrillated cellulose fibers (MFC). Preferred papermaking chemicals in the slurry include hydrophobic paper sizing agents such as AKD or ASA, wet paper strength sizing agents such as PAAE, paper sizing agents to improve the dry paper strength of the paper, such as starch, and Examples include aggregation improving agents such as cationic polyelectrolytes and cationic starch.

  As specified, the features and embodiments of the process according to the invention described above also relate to the intermediate product according to the invention.

  The present invention further includes using microfibrillated cellulose fibers (MFC) as an adsorbent for papermaking chemicals to produce an intermediate product that is added to the fibrous papermaking suspension. Examples of preferred papermaking chemicals are hydrophobic papermaking sizing agents such as AKD or ASA, wet paper strength enhancing paper sizing agents such as PAAE, paper sizing agents to improve the dry paper strength of paper such as starch, and cationic Aggregation improvers such as polyelectrolytes and cationic starch.

The common features in the examples are:
MFC, a dry cut fiber or fiber fines that has been pre-treated with (extremely) large amounts of AKD on a wide open surface area. The sizing agent that is pre-loaded into the fibrous material is introduced into the process by means of a jet-type injection (eg TrumpJet ™) type metering device. Preheating the treated fibrous material containing the yield aid provides effective yield and increases the paper strength characteristics of the paperboard.

  Jet injection occurs just before the headbox and reduces the tendency of the dissolved chemical dissolution caused by the mechanical shear forces of the PM process. The above method also allows a plug with high hydrophobicity formed by microfibrous and / or microparticles to be introduced into the paperboard structure. These hydrophobic plugs can also shield open capillary structures due to their high hydrophobicity. This combination of fiber particles with high hydrophobicity and steric hindrance can eliminate the problem (REP) associated with bulky paperboard sizing.

  On the other hand, most of the AKD is bound to the fiber carrier agglomerated particles before being introduced into the process, which is believed to automatically greatly increase the total AKD yield.

  MFC fibers pre-loaded with sizing are applied onto pure chemically untreated fiber surfaces to ensure maximum possible sizing yield and possible harm between sizing and other chemical additives Minimize unwanted interactions.

  The Z-axis and dry paper strength of the paperboard is generated by MFC, dry cutting pulp or other ridiculous fiber material pre-treated with a sizing agent (wet paper strength enhancer / dry strength enhancer) . Since the surface of these fibrous particles is loaded higher by the paper strength enhancing sizing agent, strong fiber-fiber bonds can be produced.

  The three-dimensional structure of these “pretreated particles” can form cross bondings in the bulky fiber network better than previous paper strength enhanced sizing methods. By using this method, only a portion of the fiber network material is treated with a wet paper strength enhancer or a dry paper strength enhancer. The remainder of the free fiber area may be better used, for example by hydrophobic sizing.

  High dosages of effective paper strength enhancers can be collected in the most important areas of the fiber network while increasing the bond strength to collect on selected fiber particles with high (bond) surface area. is there.

Example 1.
Paperboard was made on a pilot paperboard machine.
Finished paper 100% CTMP, 150gsm
Typical liquid packaging board chemicals (starch, two-component yield improvers, etc.)
Reference example: administration of AKD to thick paper (leveling box), 91% wire yield, 23% AKD yield
Test 1: AKD was premixed with MFC (ratio 1: 9) and administered just before the headbox (TrumpJet ™), wire yield 93%, AKD yield 29%
Test 2: Immediately prior to administration, AKD was mixed with MFC in a T-shape (ratio 1: 9) and administered just before the headbox (TrumpJet ™), wire yield 94%, AKD yield 32%
Test 3: AKD was premixed with MFC (ratio 1: 9) and mixed with C-PAM 100 g / t immediately prior to administration (TrumpJet ™), wire yield 93%, AKD yield 54%
^* ) Here, TrumpJet ™ refers to a commercial high-speed spray type drug mixing / dosing system sold by Wetend Technologies.

Example 2
The thin paper surface was prepared with a pilot paper machine.
100% finished paper exposed birch craft, 65gsm
Typical chemicals used in thin paper furnish (fillers, two-component yield improvers, etc.)
Reference example: ASA administered to short circulation (mixed pulp); Wire yield 50%
Test 1. 0.5 kg / t ASA + 0.5 kg / t MFC (TrumpJet ™ with T profile) +100 g / t C-PAM (TR2), wire yield 64%.
Test 2. 0.5 kg / t ASA + 5 kg / t MFC premix (according to TrumpJet ™) and 100 g / t T2: wire yield 64%
Test 3. 0.5 kg / t ASA + 35 kg / t dry cutting pulp premix (according to TrumpJet ™); (?) No C-PAM added: 70% wire yield

Claims (16)

A method for controlling yield on a forming fabric in a papermaking process, comprising at least:
Preparing a fiber suspension for papermaking;
A step of preparing a slurry containing fine cellulose fibers, wherein the specific surface area of the fine cellulose fibers is larger than the specific surface area of the fibers of the fibrous suspension;
Adding at least one papermaking chemical to the slurry, the papermaking chemical being a hydrophobic sizing agent, and adsorbing the papermaking chemical on the fine cellulose fibers to form an intermediate product ;
Incorporating the intermediate product into the fibrous suspension for papermaking; and feeding the fibrous suspension containing the intermediate product onto the forming fabric of a papermaking machine via a head box. seen including,
The weight of fibrillated cellulose fibers in the intermediate product is greater than the total amount of one or more papermaking chemicals in the product;
Control method.   The method of claim 1, wherein the fine cellulose fibers are fibrillated fibers having a fiber diameter of less than 200 nm.   The method of claim 2, wherein the fibrillated fibers have a fiber length of 100 nm to 200 μm.   4. A method according to claim 2 or 3, wherein the slurry comprises microfibrillated cellulose fibers (MFC).   The method according to any one of claims 1 to 4, wherein a single papermaking chemical is adsorbed so as to cover the applicable surface of the fibrillated cellulose fiber.   After the first papermaking chemical is adsorbed on a part of the applicable surface of the fibrillated cellulose fiber, the second papermaking chemical is adsorbed on the remaining part of the applicable surface of the fibrillated cellulose fiber. The method as described in any one of Claims 1-4. The weight ratio of fibrillated cellulose fibers and one or more papermaking chemicals, 20: 1 to 1: The method of claim 1 1. Prior to feeding into the forming fabric to the suspension from the headbox, according to claim 1-7 to said intermediate product is added to the short circulation of the white water being used to dilute the fiber suspension The method as described in any one of. The method according to any one of claims 1 to 7 , wherein the intermediate product is added to the fibrous suspension before the suspension is diluted with short-circulating white water. After the intermediate product pre-integration or integration into the fiber suspension, more of claims 1-9 incorporating chemicals for one or more further paper to the fiber suspension for papermaking The method according to claim 1. Before turning to the head box, the method according to any one of claims 1 to 10 for diluting the fibrous suspension, until the consistency of 1.2 wt% at most. Before injecting the intermediate product into the fibrous suspension, the fibrillated cellulose fibers are mixed with the papermaking chemical to form the intermediate product, thereby using the mixer to form the intermediate. the method according to any one of claims 1 to 11 is added to. The method of claim 12 , wherein the mixer is a jet jet mixer. An intermediate product comprising a cellulosic slurry or lignocellulosic slurry, added to a fiber suspension used in papermaking, and at least one adsorbed on the fibrillated cellulose fiber , it looks containing a papermaking chemicals are hydrophobic size, weight of the fibrillated cellulose fibers of the intermediate product is larger than the total amount of one or more papermaking chemicals in the product, the intermediate product object. The intermediate product of claim 14 , wherein the slurry comprises microfibrillated cellulose fibers (MFC). A method of using microfibrillated cellulose fibers (MFC) as an adsorbent for a hydrophobic papermaking sizing agent to produce an intermediate product added to a fiber suspension for papermaking , said intermediate product A method of use wherein the weight of fibrillated cellulose fibers therein is greater than the total amount of one or more papermaking chemicals in the product .